In the manufacture of aircraft for general aviation and in the manufacture of remote-controlled aircraft, to reduce weight, designs are still used, in which the entire body of the aircraft, or parts thereof, are made of spars and ribs. These can be made of metal, wood and/or plastic and must be covered. The coverings are preferably foils or fabrics that are applied to the structure.
The publications and other materials, including patents, used herein to illustrate the invention and, in particular, to provide additional details respecting the practice are incorporated by reference.
WO 96/14208 A1 (U.S. Pat. No. 6,548,428) discloses a foil that is suited for covering aircraft. A multilayer material is disclosed comprising a polyester carrier foil, onto which a polymer layer, based on polyurethane polymers, is applied, in addition to a pressure-sensitive adhesive layer, which is applied to the polymer layer on the side facing away from the carrier foil. This publication discloses a foil for covering aircraft constructions but not a fabric that is suited for covering.
US 20060084336 A1 discloses a multi-layer, flexible covering fabric for aircraft constructions. This fabric is made of laminated layers and distinguishes itself through especially low gas permeability. Therefore this fabric is especially intended for the construction of Zeppelins.
Furthermore, covering fabrics made of linen, cotton and polyester are known for the use of covering aircraft. These fabrics are applied with nitrocellulose adhesive or chlorinated rubber adhesive to the parts of aircraft that need to be covered, and once the adhesive dries tension is induced in the fabric. To do so the polyester fabrics are shrunk with heat and painted with a varnish. After various coats of varnish, one to two layers of silver varnish are applied for UV protection. Finally the finishing varnish is applied.
In DE 849 051 a covering of aircraft is disclosed, which comprises at least two fabric sheets lying on top of one another, with their warp threads running at an angle to one another. Each fabric sheet is individually stretched, and then connected by a treatment with resin. The fabric sheets are treated with solvent-containing impregnations and after being stretched are treated with tension inducing varnish.
The disadvantage of the fabrics and methods for their processing known from the prior art is, that in the use of polyester fabrics, although the fabric fibres are covered by nitrocellulose adhesive, the adhesive does not bind with the fibres.
Furthermore, nitrocellulose adhesives and varnishes harden further over time, which leads to the embrittlement of the entire adhesion and covering. As a result, the covering becomes vulnerable to mechanical damage and it is possible that parts of the covering become unattached without external force. Lastly, when using the solutions for covering aircraft known in the prior art, a new covering is required after some years.
A further disadvantage of the prior art solutions for the covering of aircraft lies in the uncontrolled gain of weight through the color painting and layers that are applied. In weighing a square meter of the fabric disclosed in the prior art, a gram weight variability of 100 to 400 g/m2 was measured.
Furthermore, polyester fabrics with solvent-based surface covering are known from model plane building, in which the heat sealable adhesive is applied to the back-side. The covering can comprise of a resin solution made of polyurethane or a PVC/PVA co-polymer according to GB 2 215 746 A (U.S. Pat. No. 4,997,688), wherein the resin may have cross-linking agent and catalyst colorant or metal pigment. Furthermore, polyester fabrics for aircraft with a solvent-based surface covering are known, which are distinguished by high strength, but low shrinkage and low further rip resistance. These products are adhered through heat-activatable adhesives that have the disadvantage that under high temperatures they can become soft, the covering loses tension and can even become wrinkled, or the covering can start to float on the adhesive, which significantly limits their useful properties.
Thus, there remains a need in the art to provide a covering material for aircraft that avoids one or more of the disadvantages of the prior art.
The present invention seeks to address at least aspects of said need by the features set forth herein.